Venous leg ulcers and other severe chronic wounds affect 5-7 million Americans, and are responsible for a direct cost of at least $20 billion annually. Patients with venous ulcers experience poor quality of life, frequent infections, and loss of work and independence. Clinical outcomes have improved in recent years because of better conventional care and new advanced therapies, such as the use of living bioengineered skin. However, the underlying problem of venous hypertension leads to severe secondary changes, such as tissue fibrosis, propensity for infection, and an increasingly recognized set of phenotypic changes in resident wound cells that impair dermal repair and epidermal resurfacing. Venous ulcers can become very difficult to heal. Indeed, even advanced therapies heal less than 50% of venous ulcers that have been present for more than a year. We have recently developed evidence that the topical application of autologous bone marrow-derived mesenchymal stem cells (MSCs), grown from the patients' own bone marrow aspirate and cultured and expanded in vitro, can lead to dramatic acceleration of healing in chronic wounds, including venous ulcers. During our preliminary work, we have developed a novel fibrin polymer construct for delivering the cultured MSCs to the wound in a spray system. In doing so, we modified an existing fibrin glue construct by decreasing the fibrinogen/thrombin concentrations required for polymerization and by eliminating aprotenin as the protease inhibitor component. Once sprayed into the wound, the MSCs are in a thin fibrin gel that does not affect their viability and is endogenously eliminated, thus releasing the cells to the wound. We are now ready to move forward with a clinical trial that will test the hypothesis that the patients' own MSCs can accelerate the healing of their wounds. We have developed a GMP facility for handling the the growth of MSCs, and we have received an IND from the FDA for our clinical trial. We plan the following two specific aims: 1) Determine the effect of MSCs on the healing of venous ulcers in a three-arm randomized controlled blinded clinical trial. All patients will be treated with conventional leg compression bandages. Cultured autologous MSCs will be delivered to the wound in a fibrin spray, and this group will be compared to control patients receiving leg compression treatment alone or the fibrin spray only. Healing will be assessed by computerized planimetry for wound edge migration and healing rate, wound size reduction, and complete closure; 2) Characterize and closely correlate the expression of wound edge molecular markers of impaired healing and epithelial migration in response to treatment. Baseline and sequential biopsies from the edges of venous ulcers treated in specific aim 1 will be used to determine the epidermal expression of c-myc, 2-catenin, and keratins 6/16 and 17 at the wounds' edges. These measurements, closely correlated with wound size and edge migration, will help us establish promising molecular markers involved in impaired healing and whether the MSCs may work by affecting the expression and localization of these specific molecular markers.